In this work, we will apply Los Gatos Research's ultrasensitive absorption spectroscopy technology, Off-Axis Integrated Cavity Output Spectroscopy (Off-Axis ICOS), to simultaneously and inexpensively (< $50 per sample) measure 2H, 18O, and 17O in liquid water samples. Briefly, in Off-Axis ICOS, laser light is coupled to an optical cavity in an off-axis fashion and is continuously measured similar to a standard absorption experiment (Figure 1) (1). The cavity provides an extraordinarily long effective optical pathlength (e.g. typically 5 - 10 km) allowing for the accurate quantification of weakly absorbing molecules. Moreover, since the off-axis beam path is not unique, the system is extremely insensitive to changes in alignment, making it robust. This robustness combined with the long effective optical pathlength makes it possible to measure water isotopomers with very high precision. Since its development, Los Gatos Research (LGR) and its commercial customers have performed many experiments to validate the sensitivity and robustness of Off-Axis ICOS to measure a variety of trace gases including water isotopomers H2O, 1H2HO, and H218O (2, 12, 14, 19, 26, 27) and most recently water isotopomers in undistilled human urine (3).